The present invention relates generally to and has essentially for its fubject matter a divice forming a rotary or swivel joint for a cryogenic liquid in particular applicable for the transfer of liquefied natural gas for instance off-shore at sea.
Devices forming rotary or swivel joints for a cryogenic fluid are already known. For instance, the French patent application No. 83.00 463 of the applicant discloses a device comprising a stationary part and a rotary part, each part carrying at least a corresponding duct suitable for the flow of cryogenic fluid through the joint. Moreover, such a device comprises fluid-tight or sealed heat insulating means for the vital portions of the joint in particular such as the portions located at the plane of junction between the stationary part and the rotary part in relation to the environmental medium. During off-shore transfer for instance, between a ship and a refinery unit on shore, some flowing portion of the cryogenic liquid undergoes a vaporization or boil-off. The gas thus evolved may not be rejected or exhausted to the open air and it is necessary to provide a duct for the return thereof.
Heretofore, to solve this problem, harbour appliances provided with two independent armas for the transfer of cryogenic liquid and for the return of the gas from the vaporized liquid have been designed. Such transfer constructions, however, are complicated an accordingly expensive.